There is a trend in the automobile industry to use internally adjustable reflector headlamps. Internally adjustable reflector headlamps include a reflector and bulb socket assembly enclosed within a sealed headlamp housing and lens. The orientation of the reflector within the housing is adjustable to control the direction of the light beam cast by the headlamp. Typically, the adjustable reflector is supported by three ball studs that extend from the rear of the headlamp housing and fit within sockets located on the back of the reflector. A middle ball stud is secured directly to the headlamp housing to provide a fixed pivot point for the reflector. The other two ball studs are connected to adjuster mechanisms secured to the rear of the headlamp housing. By operating the adjuster mechanisms, the ball studs can be extended and retracted to control the horizontal and vertical orientation of the reflector. Examples of such adjusters include those disclosed in U.S. Pat. Nos. 5,707,133 and 5,214,971 to Burton et al., U.S. Pat. No. 5,483,426 to Lewis et al., U.S. Pat. No. 4,796,494 to Eckenrode et al., and U.S. Pat. No. 4,703,399 to Van Duyn et al.
United States National Highway Traffic Safety Administration (“NHTSA”) standards require that horizontal adjuster mechanisms used in connection with internally adjustable reflector headlamps must be either non-readjustable after the proper aim has been achieved or be equipped with a non-recalibratable vehicle headlamp aiming device (“VHAD”) which is zeroed after the proper aim has been achieved. As such, vehicle manufacturers must either aim the lamps and provide a mechanism to prevent future readjustment, or aim the lamps and provide a non-recalibratable VHAD which is properly zeroed. One method of providing a non-recalibratable VHAD is disclosed in U.S. Pat. No. 6,042,254 to Burton (the inventor of the present invention), the disclosure of which is incorporated herein by reference. Several methods of providing a non-readjustable headlamp adjuster are disclosed in U.S. Pat. No. 6,050,712 to Burton, the disclosure of which is incorporated herein by reference.
One problem experienced when using existing adjuster devices, regardless of whether they are in compliance with NHTSA standards, is that they suffer one or a combination of the followings draw backs: excess cost; failure due to a lack of strength; failure due to corrosion; an unreliable air tight seal between the ball stud and adjuster housing allowing the entrance of contaminants into the headlamp; and size not being compact enough for some of the new aerodynamic vehicle designs in which space in the front of the vehicle is at a premium. When all or most of the adjuster parts are manufactured from metal, strength is more easily achieved but failure due to corrosion can frequently result and plating must be used in an effort to resist corrosion. Substantial corrosion in the threaded region is most detrimental because it can cause the threads to jam and become inoperative. Plating, while somewhat helpful, provides only limited resistance to corrosion and adds a significant cost. When all or most of the adjuster parts are manufactured from plastic, inadequate strength or stiffness can be an issue when trying to provide a design with a compact size. For instance, plastic gears using conventional gear tooth designs can easily strip, especially if the gears are inadequately supported within the adjuster housing. This stripping most easily occurs when the device is “over adjusted” beyond the designed travel capabilities of the adjuster mechanism. Conventional gear tooth designs use equal tooth thickness on both gears which does not maximize stripping resistance if the material strength of one gear is greater than the other. Further, many existing adjuster housing designs lack adequate gear support to prevent the gears from partially or fully separating under high torque conditions. When the gears separate under torque the gear teeth are not fully engaged and stripping resistance is reduced. Accordingly, a need exists for an adjuster that is in accordance with NHTSA standards and is low cost, compact in design, prevents failure due to corrosion, has a reliable air-tight seal to the headlamp, and resists stripping and failure of internal components.